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As flame-retardant Polyacrylonitrile (PAN) fibers was one of the most important differential fibers, it was of great importance to make research on the modification of flame-retardant PAN fibers to improve its characteristics. In this present study, the flame-retardant PAN fiber with good moisture absorption and mechanical properties has been prepared treated by blending solution of sodium hydroxide and hydrazine hydrate. FTIR spectra presented that new amide and cyclization-crosslinking pyridine group band peaks appeared. X-ray diffraction showed that the crystal structure of PAN fibers has been converted from quasi-crystalline structure into partially crystallized structure after modification treatment. SEM micrographs indicated that the original longitudinal surface microgroove has changed to layered structure by surficial etchant.

The temperature stability of scale factor (SF) has been analyzed and tested systematically for an optical voltage sensor (OVS) based on Pockels effect in this paper. The cardinal temperature sensitive parameters in sensor head and their impacts on SF are brought out by theoretical analysis and simulation method. Corresponding experiments are arranged to verify the validity of theoretical analysis. A real-time temperature compensation system is fabricated to reduce the error of SF in temperature fluctuation environment and its effectiveness is certified by experiment.

This paper provides a review of fiber optic pipeline monitoring sensors development over recent decades. We analyze pipeline monitoring sensors based upon different optical techniques, such as Sagnac effect, Brillouin & Raman backscattering, fiber Bragg grating, Mach-Zehnder interference and OTDR (Rayleigh backscattering). We present theoretical principles & experimental achievements by the different techniques and analyze the advantages & weaknesses for each technique. Finally, some future research directions in this research field are discussed.

A Mach-Zehnder interferometer based fiber-optic distributed disturbance sensor (FDDS) incorporating a modified phase generation carrier (PGC) is proposed and investigated. It is found that the slow time-varying fluctuation such as temperature variation causes the location errors. By employing a modified PGC technique that satisfies the requirements including high sampling frequency and compensation of the time delay from the long length fiber, the location errors caused by the slow time-varying fluctuation can be eliminated.